The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Berries off Aust shelves after Hep A scare

A popular brand of frozen berries will be pulled from the shelves of major Australian supermarkets after it was linked to infections of Hepatitis A.

Patties Foods, the distributor of 1kg packets of Nanna's Frozen Mixed Berry, issued a nationwide consumer recall on Saturday just hours after Victoria's health department urged people to dump the product immediately.

Four adults, three in Victoria and one in NSW, have contracted the potentially deadly Hepatitis A virus after consuming the imported fruit.

The uncommon infection is normally associated with travel to affected countries, but the only link between the recent Australian cases is the frozen berry mix which is sold at Woolworths, Coles and IGA stores around the country.

It contains strawberries, raspberries and blackberries from China and blueberries from Chile.

The product is packed in China, but distributed by Victoria-based Patties Foods.

Patties says detailed testing of the product is being carried out, with grocery stores also advised to pull it off shelves.

"Patties Foods advises consumers not to eat the product, and return packs to the place of purchase for a full cash refund," the company said in a statement.

Hepatitis A is spread when traces of faecal matter containing the virus come in contact with hands, water or food and then enter a person's mouth.

Dr Finn Romanes, from Victoria's health department, said frozen berries have been linked to Hepatitis A in the past.

He said more cases of the virus could come forward after the product warning hit news on Saturday.

"It is possible people have this product in their fridges and freezers right now," he told reporters.

Dr Romanes said the latest contamination would have occurred overseas, before the product was imported.

Symptoms of Hepatitis A include abdominal pain, nausea and fever as well as yellow skin and eyes.

The consumer recall applies to all 1kg packs of Nanna's Mixed Berries with a Best Before Date up to and including November 22, 2016.

No other Nanna's or Patties Foods products are affected.

It comes as a number of Victorian hospitals are told to dispose of chocolate mousse, which has been found to contain listeria.

Hospitals are contacting patients who might have consumed the dessert recently, though no cases of illness have been reported and the product is not supplied to the public.

The contamination came to light after the company conducted routine testing of its products.

Listeria is particularly dangerous for pregnant women, their unborn babies and the elderly.